Single track railway signal systems using normally deenergized coded track circuits



June 19. 1956 T. w. TIZZARD 2,751,491

SINGLE TRACK RAILWAY SIGNAL SYSTEMS USING NORMALLY DEENERGIZED CODEDTRACK CIRCUITS Filed Sept. 6, 1951 4 Sheets-Sheet 1 Ill-I'lllllallllllll w it INVENTOR. 7720112025 W Tz'zzard HIS ATTORNEY EN ww wwESE u M5 T. w. TIZZARD 2,751,491 smcm: TRACK RAILWAY SIGNAL SYSTEMS usmcNORMALLY DEENERGIZED CODED TRACK CIRCUITS 4 Sheets-Sheet 2 June 19. 1956Filed Sept. 6, 1951 d W m z w M w QM; VT R w 1 m r m A m w m T v. H B a?w Wx RQUWWSP L ng K? ksmwaw \Gkw mmfi i Y E; Rink m as IImM L \Q\ Ev H rs xmfl i g IMNQQ 1 N kw ww wx n 0 BQQ m hm June 19. 1956 T. w. TlZZARD2,751,491

SINGLE TRACK RAILWAY SIGNAL SYSTEMS USING NORMALLY DEENERGIZED CODEDTRACK CIRCUITS Flled Sept 6 1951 4 Sheets-Sheet 3 E REES INVENTOR.Thomas W Tizzard HIS ATTORNEY 4 Sheets-Sheet 4 T. W. TIZZARD |i EB wwsmE 9s m SINGLE TRACK RAILWAY SIGNAL SYSTEMS USING NORMALLY DEENERGIZEDCODED TRACK CIRCUITS June 19. 1956 Filed Sept. 6, 1951 INVENTOR. ThomasW fizza'rd BY HIS flTTORNZ'Y United States Patent O SINGLE TRACK RAILWAYSIGNAL SYSTEMS USING NORMALLY DEENERGIZED CODED TRACK CIRCUITSApplication September 6, 1951, Serial No. 245,284

11 Claims. (Cl. 2463) My invention relates to single track railwaysignal systems using normally deenergized coded track circuits, and moreparticularly to such a signal system wherein the direction of trafiic isestablished and the signals are controlled through a centralized trafficcontrol or other remote control system.

An object of my invention is the provision of an improved single tracktwo direction railway signal system using normally deenergized codedtrack circuits.

Another object of my invention is the provision of a single track twodirection railway signal system using normally deenergized coded trackcircuits which enable the direction of tratlic to be established and thesignals to be controlled by means of a simplified or modified form ofcentralized t'rafiic control system.

A further object of my invention is the provision of a railway signalsystem of the type here involved wherein the control and indicationcodes of selected signals associated with a field station of acentralized traffic control system are transmitted through coded trackcircuits.

A more specific feature of my invention is the provision of a railwaysignal system of the type contemplated, incorporating novel means forcontrol and indication of a passing siding leaving signal and a takesiding signal from a field station of a centralized traffic controlsystem through coded track circuits.

Other objects, features and advantages of my invention will appear asthe specification progresses.

The foregoing objects, features and advantages of my invention areattained by the provision of a single track two direction signal systemhaving normally deenergized reversible coded track circuits arranged topermit the eascading of a control from one track circuit to the next. Astretch of a single track railway is formed with a train block whichpreferably includes a given end of a passing siding, the main trackalong this passing siding and the stretch of single track to the nearend of the next passing siding. This block is formed in track sectionswhich are provided with coded track circuits that are arranged in such amanner as to enable the direction of traflic through the block to beestablished by a modified or so-called single end control form ofcentralized traflic control system. That is, the given end of thepassing siding is provided with the conventional group of four waysidesignals and a power switch operating mechanism'of an associated fieldstation of a centralized traflic control system. The other end of thispassing siding is not provided with the conventional signals but isprovided with a spring switch mechanism, a take siding indicator orsignal and a siding leaving signal. The spring switch mechanism herecontemplated is of the type by which the switch points are positivelylocked in their normal position for bodies my invention.

facing point moves over the switch and which become automaticallyunlocked when a train trails through the switch. Also, this switchmechanism includes a lever whereby the switch can be thrown to itsnormal and reverse positions manually. These spring switch mechanismsare well known in the art and in wide commercial 2PS and 6P8,respectively, and are relatively short.

Fatented June 19, 1956 use. One such type of spring switch mechanism isshown and described in Letters Patent of the United States No.1,976,827, granted October 16, 1934, to Herbert L. Bone. The sidingleaving signal is of a standard type adapted to display clear, approachand stop indications for governing train movements from the sidingthroughthe spring switch and track block. The take siding signalcomprises a lamp which is normally dark and which when illuminatedcauses the display of a symbol, preferably in the form of the letter Sto convey the instruction to a train approaching the spring switch tostop and reverse the switch by hand and move into the siding. It is tobeunderstood that instead of the spring switch mechanism the switch may beprovided with a mechanism governed by an approaching train.

According to my invention no field station and associated apparatus ofthe centralized traffic control are provided at the spring switch end ofthe passing siding and the siding leaving signal and the take sidingsignal are controlled and indicated through the field station located atthe selected end of the passing siding by means of codes transmittedthrough coded track circuits.

The stretch of track between the passing sidings is provided withintermediate wayside signals which are automatically controlled by thecoded track circuits in such a manner as to permit following moves.

I shall describe one form of apparatus embodying my invention when usedin a signal system for a stretch of single track railway extending froma selected end of a passing siding along the passing siding and throughthe stretch of single track to the near end of the next adjacent passingsiding, and shall then point out the novel features thereof in claims.

The accompanying drawings, Figs. 1a to 1d, inclusive, when placed end toend with Fig. In at the left, are schematic views showing one form ofapparatus embodying my invention when applied to a stretch of singletrack railway which, as stated hereinbefore, includes a selected end ofa passing siding, the main track along this passing siding and thestretch of track to the near end of the next adjacent passing siding.

Similar reference characters refer to similar parts in each of theviews.

In the drawings, the reference characters 1a and 1b designate the trackrails of a stretch of single track railway extending from location 2 atthe left-hand or West end of a passing siding 2P5 to a location 6 at thelefthand or West end of the next passing siding 6P8 to the east. Thisstretch of track forms a track block through which trafiic moves in bothdirections under the direction of wayside signals the control apparatusfor which em- The track rails 1a and 1b of the main track of this blockare formed by the usual insulated rail joints with track sections 2T,3T, 4T, 5T and 6T. The sections 2T and 6T include the track switches atthe west end of the sidings The sections 3T, 4T and ST are relativelylong and may be of the maximum length permissible for track circuits ofthe type here involved.

It is to be noted that the track rails of the siding 2P5 are formed byinsulated rail joints with a short track section 4AT which providesapproach control of a siding leaving signal 4R to be describedhereinafter.

Each track section is provided with a track circuit. The track circuitsfor the short sections 2T and GT are of the conventional normallyenergized direct current type and each circuit is provided with a trackbattery connected across the rails at one end of the section and adirect current track relay connected across the rails at the other endof the section as will be apparent from an inspection of the drawings.The track section 4AT for i track relay, and a coding or codetransmitting relay at each end of the section. Each of the codefollowing track relays is identified by the reference character CF plusa prefix corresponding to the section and direction of traffic withwhich the relay is related. Each of these code following relays is ofthe polar biased type well known in the art and it is sufiicient forthis application to point.

out that thesepolar code following relays are provided with an armaturewhich is biased to a released position closing back contacts, isretained in this released position when current flows in the relaywinding in one direction, and the armature is picked up closing frontcontacts only when current flows in the relay windings in the otherdirection. In the drawings each of the polar biased code followingrelays assumes a picked up position only when current flows from thepositive terminal of the track battery through the relay winding in thedirection indicated by an arrow placed on the relay winding. Each of thecoding or code transmitting relays is a direct current relay having acontact operable to a first and a second position'at a ratecorresponding to the rate of code pulses supplied to the relay winding.These code transmitting relays of the track circuits are identified bythe reference character CTP plus a prefix corresponding to the tracksection and the direction of traflic with which the relay is associated.

' The wayside signals provided for governing traffic through the blockmay be any standard type of wayside signal and the signals areidentified by a number corresponding to its location plus a suffix L orR to correspond to the direction of trafiic, left or right, governed bythe Signal. These wayside signals are shown as being of the;searchlight'typereach having a three position mechanism identified bythe reference character G prefixed by the corresponding signalidentification. It is to be noted that these signal mechanisms are sopolarized and connected to controller contacts, which are operativelyconnected to the mechanism as indicated in the drawings by dotted lines,'for a left-hand contact as viewed in the drawing to close a frontcontact when the signal is operated to display a green or clear signalindication, and, a right-hand contact to close a front contact when thesignal is operated to display a yellow or approach signal indication.Also the two contacts are moved to a lower position closing backcontacts when the mechanism is deenergiz ed and the signal displays ared or a stop signal indication. V

Itisto be pointed out that a wayside signal 4L, to be referred to morefully hereinafter, is mounted on the same mast as a signal SL. Thesignal 4L comprises a lamp which is normally dark and which whenilluminated causes the display of an illuminated letter S foratakesiding signal, this signal being used to convey the instruction toa train. that it is to move to the siding 2P8 by hand throwing theswitch 3W.

Inasmuch as my invention relates to the wayside signal apparatus, thecentralized trafiic control system by means of which the track circuitsand signals are controlled from a central ofiice is shown onlyconventionally because such centralized trafiic control system may beany one of several well-known arrangements by which control relays atdifierent wayside field stations along a railway are selectivelycontrolled from a centralfofiice. For a full understanding of myinvention it is sufiicient to point out only that currents of difierent'codes are transmitted from a central office to different field stations.These codes preselectthe field station and also preselect the control tobe effected atthe selected station and these controls are carried out atthe field station by certain terminals being supplied with positiveenergy. In the drawings a field station 2FS is located at'the location 2and a field station (SP5 is provided at the location 6. Furthermore,each field station apparatus includes means by which indication codesare generated and transmitted from that field station to thecentraloflice in response to positive energy being applied to certainother terminals of the apparatus. The transmitting medium between theoflice and these field stations is usually a two wire line circuit butit is apparent that transmission may be effected by space radio and myinvention is not limited to any specific form of transmitting mediumbetween the remote otlice and the different field stations of the remotecontrol system here involved.

The codes for the different track circuits are generated by 'codetransmitters or coders designated by the reference character CT'plus anumeral 75, 120, 01-180 to designate the code rate of its operation.,These code transmitters may take different forms and preferably are ofthe pen dulum type which when energized operate contacts'periodically ata rate of 75, or times per minute.

It is to be understood that these code rates are used by way ofillustration and other code rates can be used. These code transmittersare used to periodically interrupt a circuit by which current pulses aresupplied to the coding or code transmitting relays referred tohereinbefore and'thereby cause the corresponding code rate of operationof these relays.

It is to be noted that current sources other than the track batteriesare provided at the different locations. These current sources arepreferably batteries notshownbut which are identified in the drawings bythe positive and negative term'mals of the sources being identified bythe reference characters B and N, respectively. 7

The apparatus employs slow release relays at many places as will appearfrom time to time in the specification. These slow release relays may beprovided .with slow release characteristics in any of the several waysknown to the art and in the drawings the slow release characteristic isindicated by an arrow at the relay contact.

Furthermore, the apparatus includes decoding units which are selectivelyresponsive to the different code rates. of the track circuit current.These decodingunitsrare indicated conventionally in the drawings by arectangle DU with an identification numeral 120 or 180 to indicate the.corresponding code rate to which the 'unit responds.-

These decoding units are shown conventionally because 7 their specificstructure forms no part of my invention and the. structure may be of anyof the standard arrangements known to. the art. It is, sufiicient forthis application to point out that; these decoding units includeinductance. and capacitance tuned toresonance at the frequency of thecode rate to which it responds so that a direct current relay connectedto. the output of the decoding unit is' efiectively energized and pickedup only when the unit is supplied with current pulses at thecorresponding fre-r quency.

The power switch machines at the locations 2 and 6 for operating thetrack switches for the corresponding end of the passing sidings 2PS- and6P8, respectively, are shown conventionally at- ZWM and 6WM' by thesymbol commonly employed to designate such mechanism; and the circuitsfor these mechanisms are not shown because their points to thenormal orreverse position and to lock the,

switch points in these positions.

, It is believed that the wayside apparatusembodying my invention asthus described can be fully understood from a description of theoperation of the apparatus under different assumed traflic conditions.In describing the operation of the apparatus, I shall assume first thatthe apparatus is in its normal condition, that is, the condition itoccupies when no train occupies the track block. Under this normalcondition, the apparatus is positioned as shown in the drawings and thetrack circuits for the sections 3T, 4T and ST are deenergized but thetrack circuits for the short sections 2T and 6T are constantly energizedand their corresponding track relays 2TR and 6TR are picked up.Furthermore, the code transmitters 75CT, 120CT and 180CT at the location2 and code transmitters 750T and 180CT at location 6 are constantlysupplied with power and operating.

1 shall next assume that with the apparatus in its normal condition itis desired to establish the direction of traffic from left to right,that is, eastbound, and to clear the signal 2RA to permit a train tomove east through the block. The first step would be for the operator ofthe centralized traflic control system to send from the oifice to thefield stations 2FS and 6FS control codes which at field station 2FSprepare a circuit for control of the signal 2RA and which at the fieldstation 6FS cause coded energy to be supplied to the track circuit forcascading through the track circuits to the location 2 to check thenonoccupancy of the block. This control at station 2FS will causepositive energy'to appear at a terminal 11 of the field station and towhich terminal a relay ZRGZ is connected with the result the relay ispicked up. Subsequent to the control energy at terminal 11, the relayZRGZ is controlled by a stick circuit which includes its own frontcontact 12 and terminal 13 of the field station apparatus and to whichterminal energy is applied by the usual circuit network, not shown. Withthe relay 2RGZ picked up closing front contact 18, a control circuitnetwork is prepared for governing the signal 2RA and which network willbe referred to shortly.

At the field station 6FS this control code will cause positive energy toappear at a terminal 20 of the field station unit and to which terminala relay 6WFR is connected with the result this relay is picked up.Subsequent to the control energy at terminal 20 the relay 6WFR isretained energized by the usual stick circuit which includes its ownfront contact 21 and terminal 22 of the field station unit and to whichterminal positive energy is supplied in the usual manner.

Since the wayside signal 6RA which governs eastbound trafiic at location6 is normally set to display stop, a repeater relay 6RGY connected tocontacts of the controller of this signal is deenergized and a circuitis prepared by which pulses of the 75 code rate are supplied to a codetransmitting relay SWCTP for the track circuit of section T, thiscircuit including terminal B of the power source, contact 23 of the codetransmitter 75CT at location 6, back contact 24 of relay 6RGY,- frontcontact 25 of the now energized directional relay GWFR, winding of relaySWCTP and terminal N of the power source. It follows that this codetransmitting relay is now operated at the 75 code rate so that pulses ofcurrent from a battery B5B are supplied to the track circuit of thesection 5T, the circuit being completed from the positive terminal ofbattery B5B through resistor 26, front contact 27 of the coding relaySWCTP, front contact 28 of the directional relay 6WFR, lead wire 29 torail 1a of section ST, and from rail 1b of that section by lead Wire 30to the negative terminal of the track battery BSE. These track circuitpulses are transmitted to the left-hand end of the section ST and flowthrough a connection that can be traced from rail 1a of section 5T overback contact 31 of a relay SEFR, winding of code following relay SECF inthe direction of the arrow, and wire 32 to rail 1b. Consequently thecode following relay SECF is now operated at the 75 code rate causing arelay SRH to be energized through a decoding transformer SDT,Specifically, current pulses are alternately supplied to'the twoportions of primary winding 35 of the transformer SDT through front andback contacts 7 of the code following relay SECF, and inducecorresponding voltages in secondary winding 33 of the transformer. Thesevoltages are rectified by the operation of contact 34 of the codefollowing relay and rectified current is supplied to energize the relaySRH as will be apparent by an inspection of the drawing.

Since the control relay 5RH is provided with slow releasecharacteristics, it is retained picked up by this code operation of thecode following relaySECF and the closing of front contacts 36 and 37 ofthe relay SRH completes a circuit for energizing the mechanism 5RG of asignal 5R, the circuit for the mechanism 5RG being completed throughpole changing contacts 38 and 39 of a relay 5RD, to be referred toshortly. The polarity of the current causes the mechanism 5R6 to beoperated for signal 5R to display an approach signal indication when thecorresponding lamp 40 of the signal is lighted in a manner to appearhereinafter. v

The picking up of the relay SRH also completes a circuit for adirectional relay SWFR at this location, the

circuit extending from terminal B through back contact 43 of relay SEFR,front contact 44 of relay SRH and winding of relay SWFR to terminal N.With the directional relay SWFR energized closing front contact 45, asimple circuit is closed for energizing a code transmitter CT. A circuitfor a code transmitting relay 4WCTP for the track circuit of section 4Tis now completed and current pulses fiow from terminal B through contact46 of the 180CT coder, from contact 42 of relay SGY, front contact 48 ofrelay SWFR and winding of relay 4WCTP to terminal N. It is to be notedthat relay SGY which is controlled over front contact 41 of thecontroller of signal SR is energized at this time due to the operationof the signal mechanism SRG. With the coding relay 4WCTP operated at the180 code rate, current pulses of the corresponding rate are suppliedfrom track battery B4B to the track circuit of section 4T, theconnection extending from the positive terminal of battery B4B throughresistor 49, winding of an approach relay 4EA, front contact 50 ofcoding relay 4WCTP, front contact 51 of directional relay SWFR, and leadwire 52 to rail 1a, the other side of the circuit extending from rail 1bto the negative terminal of battery B4E over lead wire 53. i It is to bepointed out that these track circuit pulses flow in the winding of theapproach relay 4EA in the direction indicated by the arrow and energizethe relay in the proper direction to pick up the relay but the relay isadjusted so that the magnitude of the current pulses is ineffective topick up the relay when the section is unoccupied and the relay iseffectively energized and picked up only when the current impulsesareincreased in their magnitude in a manner to appear later.

These pulses of track circuit current supplied at the right-hand end ofthe section 4T are received at the lefthand end of the section and flowthrough a connection to the rails of section 3T, one side of theconnection including lead wire 54, back contact 55 of a relay 4WTP, tobe referred to, front contact 56 of a relay 4RM, and wire 57 to rail inof the track section 3T. The other side of the connection extends fromthe rail 1b of section 4T to rail 1b of section 3T through wire 58, backcontact 59 of relay 4WTP, and wire 60. It follows that the track circuitpulses of the 180 code rate supplied to section 4T are by-passed aroundthe insulated joints between section 4T and section 3T and are suppliedto the rails of the section 3T. It should be pointed out that a portionof the current supplied from. the section 4T to the section 3T flowsthrough back contact 61 of a relay 3WCTP, to be referred to later, andthe winding of a polar code following relay 3ECF, whichis effectivelycon- 7' nec'ited across the rails of section 4T at this time, but

that the current flows in the winding of this codelfollowing relay inthe direction opposite to that to which the relay responds.

The current pulses supplied to the section ST in the manner justdescribed flow in the rails to the left-hand end of the section 3T andthere how in a connection that can be'traced from rail 1a through leadwire 19, back contact 14 of a relay 4GZP, to be referred to, backcontact 9 of a relay ZEFR, winding of a 'code following relay 2RCF inthe direction indicated by the arrow, back contact 8 of relay ZEFR, backcontact 16 of relay 4GZP, and lead wire 17 to rail 1b. Thus thesecurrent pulses cause the code following relay 2RCF to be operated at theI80code rate. Operation of the contact 62 of this code following relaycauses current pulses to be alternately supplied to the two portions ofwinding 63 of decoding transformer3DT and corresponding voltages areinduced in secondary winding 64 of the transformer. These voltages arerectified by the operation of contact 65 of the code following relayZRCF and applied to a relay ZRAH, with the result the relay ZRAH isenergized and picked up and retained picked up due to its slow releasecharacteristics. Furthermore, operation of contact 62 of the codefollowing relay ZRCF causes current pulses of the 180 code rate tobeapplied to the ISODU decoding unit at location 2 with the result therelay 180CP connected to that unit is effectively energized and pickedup, closing its front contact 131 and causing the relay ZRAD' to beenergized by a simple circuit easily traced. With both relays ZRAH andZRAD picked up, a circuit is completed for supplying current to themechanism 2RAG of the signal 2RA, the current being of normal polaritydue to relay ZRAD being picked up, so that the signal c is operated toindicate a clear signal aspect. Specifically, the circuit network of thesignal mechanism ZRAG in cludes terminal B of the power source, frontcontact 18 of the remote controlled relay ZRGZ, wire 5, the approachlocking and other controls usually provided but which a'ren'ot shown butindicated by a dotted portion of wire 5 due to these controls notforming a part of my present invention, front contacts 66 and 69 ofrelays ZRAH and ZRAD, respectively, signal mechanism'2RAG, front contacts 68 and 67 of relays 2RAD and ZRAH, respectively, and terminal N ofthe power source. At this time the lamp 70 of the signal 2RA is providedwith an energizing circuit not shown, but which would be of the standardform and signal 2RA displays a green light as a clear signal to permit atrain to enter the block.

For an indication of this position of signal ZRA, it is to be pointedout that with the mechanism ZRAG moved to its clear position, theclosing of contact 71 of its controller completes a simple circuit foran indication relay ZRAGY. With relay ZRAGY picked up closing itscontact 72, a connection by which energy is applied to a terminal 73 ofthe centralized traffic control apparatus at station 2FS is completedand the centralized traflic control system is caused to transmit anindication code to the ofiice for indicating this clear position ofsignal 2RA.

As the eastbound train movespast signal 2RA to enter the section 2T, thetrack relay 2TR is shunted and this relay on releasing would open thecircuit control previously mentioned for the signal mechanism ZRAG, withthe result the signal is deenergized and set to display a stopindication. When the head end of the train enters section 3T, theshunting ofthis track circuit causes the code following relay ZRCF tocease operation with the result the two relays 2RAH and ZRAD aredeenergized and released opening the circuit for the signal mechanismZRAG at other points.

' ,As this eastbound train moves from section 3T into section 4T, thecode pulses are still shunted and no further action takes place at thelocation 2. When the head end of the train reaches a reasonable distancefrom the signal 5R,the magnitude of the track end is increased due tothe shunting out of the impedance offthe track rails with the result theapproachrelay 4AE 'is efi'ectively energized and begins to follow'thecode and causes a repeater relay 4EAP to be energized and picked up by'asimple circuit including front contact 127 of relay 4EA, the relay 4EAPbeing retained picked updue' to its slow release characteristic. Theclosing'of front contact 123 of the repeater 4EAP completes a simplecircuit for the lamp 40 of the signal SR and the signal 53 displays anapproach indication to the eastbound train; j

The closing of front contact 74 'of the approach relay 4E'AP prepares acircuit for a directional stick relay SRSR so that when the train passesinto the sectionST' SRSR is provided with a pickup circuit that includesterminal B, back contact 75 of a relay SLSR, front con tact 74 of relay4EAP, back contact 76 of relay 'SRH, winding of relay SRSR and terminalN; The relay 5RSR when picked up is retained energized over a stickcircuit including its'own from contact 77 and back contact 76 of relaySRH. Since the directional stick relay SRSR is retained energizedwhilecthe train occupies the section 5T, it follows that when the trainvacatesthe section 4T the directional relay SWFR is retained ener gizedby a circuit completed at back contact 43 of relay SEFR and frontcontact 78 of the stick relay SRSR. From this it is to be seen that acoder 75CT at the loca-, tion of signal 5R is provided with anenergizing circuit completed at front contact of the relay SWFR and thecode transmitting relay 4WCTP is energized by pulses ofthe 7 51code ratedue to a circuit completed from terminal B through front contact 79 ofcoder CT, back contact 42 of relay 5GY, front contact 48 of directionalrelay SWFR, and winding of relay 4WCTP to terminal N. This results inthe track circuit for the section 4T and in turn the section 3T beingsupplied with current pulses of the 75 code rate and the code followingrelay ZRCF at the location 2 is operated at the 75 code rate causing therelay- ZRAH to be picked up closing front contacts 66 and 67. This.prepares the energizing circuitfor the signal mechanism 2RAG so that thesignalZRA can be operated to permit a following train to enter the blockin the event a control code is sent to the field station 2FS through thecentralized tralfic control system to again pick up relay ZRGZ, thisrelay having been dc energized in the usual manner when the first trainentered the block. 7

' I shall assume, however, that no following train movements are madeand the first train advances east'through the section 5T. Furthermore, Ishall assume that con-c clitions in advance of the signal 6RA east ofthe block and is cleared to permit the train to move out of the blockthrough the section 6T. up the traffic through the block the directionalrelay 6WFR at location 6 is energized through the centralized trafhccontrol station and then retained energized by a stick circuit whichincludes its own front contact 21 and terminal 22 of the centralizedtraffic control equipment. The arrangement is such'that the usualcircuit network by which energy is applied to the terminal 22 to retainthe directional relay 6WFR energized, causes this relay to-be energizeduntil the train has vacated the section (T. This condition causescurrent of the 75 code to be supplied to the section 51 while the rearof the train is passing through section 6T due to the operation of thecoding relay SWCTP by current pulses supplied through back contact 24 ofrelay 6RGY and contact 23 of the coder 75CT. That is, coded current issupplied to section ET for a brief period subsequent to the trainvacating section'ST. This 75* code -applied tothe track SeetionST Itwill be recalled that to set causes the code following relay SECF at thesignal R to be operated and the relay SRH to be picked up for a briefperiod. With relay 5RH picked up, then the stick circuit for the stickrelay SRSR is opened at back con tact 76 of relay SRH and relay SRSR isreleased to re move the supply of coded track circuit current from thesection 4T and thus the track circuits for the section 4'1 and in turnfor the section 3T are restored to their normal deenergized condition.Then, subsequent to the release of the relay 6WFR at location 6 theoperation of the coding relay SWCTP is discontinued and the trackcircuit for section ST is restored to its normal deenergized condition.

It should be pointed out in connection with the operation of theapparatus for eastbound traffic that in the event the signal 6RA iscleared prior to the clearing of the signal 2RA to permit a train tomove through the block, then the energizing of the relay 6RGY atlocation 6, due to the closing of either contact 124 or 125 of thecontroller of the mechanism GRAG, selects the code transmitter 180CT andoperation of contact 126 of this code transmitter causes correspondingoperation of coding relay SWCTP with the result current pulses of the180 7 code are supplied to the track circuit of section 5T. With thecode following relay SECF at signal 5R operated at the 180 code, thenthe relay 5RD which is controlled through the 180DU decoding unit ispicked up and the signal mechanism 5RG for the signal SR is energized bycurrent of normal polarity and this signal is operated to display aclear signal indication. With the signal mechanism 5RG energized atnormal polarity closing front contact 47, then the circuit for operatingthe coding relay 4WCT P for the section 4T includes the contact 46 ofthe 180CT code transmitter and the current pulses supplied to thesection 4T and in turn to the section 3T are of the 180 code rate thesame as previously explained.

I shall next assume that with the apparatus in its normal condition thesignal 4R is to be cleared to permit a train on the siding 2PS to trailthrough the spring switch 3W and move through the block. The operator ofthe centralized trafiic control system sends codes which at the fieldstation 6FS cause the relay 6WFR to be picked up in the same manner asdescribed for the first train and track circuit current is applied tothe section ST in the manner previously described. This time the codesent to the field station ZFS causes positive energy to appear atterminal 80 to which a relay 4RGZ is connected and this relay is pickedup closing front contacts 81 and 82 over which two stick relays 4GZP and4RGZP are energized and picked up. To provide the relay 4RGZ with astick circuit for retaining the relay energized subsequent to the remotecontrol which energizes relay 4RGZ, a relay 461 is provided and whichrelay is energized by means of a circuit completed at front contact 83of relay 4GZP and back contact 84 of an indication relay 46K to bereferred to later, and relay 461 completes at its front contact 140 astick circuit for the relay 4RGZ, this circuit including front contact144 of relay 4RGZ, back contact 145 of a relay 4LGZ, front contact 140of relay 4G1 and back contact 141 of a relay 468 to be referred tolater. The relays 4GZP and 4RGZP are provided also with stick circuitswhich are similar and which for relay 4GZP includes front contact 85 ofthat relay, front contact 86 of relay 4GK, and back contact 146 of relay468. The stick circuit for the other relay 4RGZP is similar and includesits own front contact 147 and the previously traced stick circuit forthe relay 4GZP.

With the two relays 4GZP and 4RGZP picked up due to the remote controlof relay 4RGZ, a coding relay 3ECTP at location 2 is operated at the 75code by the 75CT code transmitter, the circuit connection includingterminal B, contact 185 of coder 75CT, front contact 186 of relay 4RGZP,front contact 87 of relay 4GZP,

front contact 88 of an approach locking relay ZRMR which is preferablyprovided at location 2 in accordance to general practice but the controlof which is no part of my invention, front contact 89 of track relayZTR, winding of relay 3ECTP and terminal N. This operation of the codingrelay SECTP causes current impulses of the 75 code to be supplied frombattery B3W to the track circuit for the section 3T, the connectionextending from the positive terminal of battery B3W through frontcontact 90 of the coding relay SECTP, winding of code following relay3WCF in the direction reverse to that indicated by the arrow, frontcontact 91 of relay 4RGZP, front contact 16 of relay 4GZP, front contact16 of relay 4GZP and Wire 17 to rail 1b of section 3T and the connectionextending from rail 1:: over Wire 19, front contact 14 of relay 4GZP,front contact 92 of relay 4RGZP and to the negative terminal of battery133W. These track circuit pulses are of reverse polarity, that is, theyare of a polarity wherein the rail 1b is positive with respect to therail 1a, whereas the current pulses cascaded through the block causerail in to be the positive rail.

At the right-hand end of the section 3T, that is, at the location of thetrack switch 3W, these track circuit pulses of the reverse polarity flowin the connection extending from rail 111 through the code followingrelay 3ECF in the direction indicated by the arrow, back contact 61 ofrelay 3WCTP and wire 57 to rail la. This operation of the relay 3ECFcauses current to be alternately supplied to the two portions of winding192 of decoding transformer 4DT through contact 148 of the codefollowing relay and the voltages induced in the winding 93 of thattransformer to be rectified at contact 128 of the code following relayand applied to relay 4WTP to pick up that relay, the relay beingretained picked up due to its slow release characteristics.

This energizing of the relay 4WTP switches the con: nection of the trackcircuit for section 4T from the rails of the section 3T to a codefollowing relay 4RCF with the result that the coded track circuitcurrent applied to the section 5T at location 6 and cascaded through thetrack circuits of the block in the manner described for the first trainare now applied from the rails of section 4T to the code following relay4RCF, the connection including wire 54 leading from rail 1a throughfront contact 55 of relay 4WTP, winding of relay 4RCF, front contact 59of relay 4WTP and wire 58 to rail 1b of sec tion 4T. Consequently, thecode following relay 4RCF is now operated in response to the codedcurrent cascaded through the block and operation of the relay 4RCFcauses current to be alternately supplied to the two half portions ofwinding 95 of decoding transformer 4ADT through contact 94 with theresult a corresponding voltage is induced in secondary winding 96 ofthat transformer. This induced voltage is rectified at contact 97 of thecode following relay and rectified current applied to relay 4RH causingthat relay to be picked up and retained picked up due to its slowrelease characteristic. Furthermore, the voltages induced in transformerwinding 96 are also applied to the DU decoding unit at this location andthe corresponding relay 180CP is energized and picked up closing frontcontact 197 to complete a simple circuit for energizing a signal controlrelay 4RD. With the two relays 4RH and 4RD picked up then the signalmechanism 4R6 is provided with a con trol circuit that includes thefront contacts 98 and 99 of relay 4RH and front contacts and 101 of therelay 4RD with the result the mechanism 4RG is energized at normalpolarity and the mechanism operated to its clear position. When thetrain on the siding 2P8 moves to occupy the approach section 4AT so thatthe track relay 4ATR is energized closing front contact 103 a simplecircuit for lighting lamp 102 of signal 4R is closed and the signal 4Rdisplays a clear signal indication to permit the 11 train to movethrough the spring switch and the track block. a

It is to be pointed out that when the signal mechanism 4RG operates toits clear position closing contact 104 of its controller, a simplecircuit is provided for the signal repeater relay 4RGY and that relay ispicked up closing front contact 105 with the result that voltage inducedin the winding 106 of the decoding transformer 4DT' due to operation ofthe code following relay SECF causes cur rent to flow in primary winding167 of a transformer 108 and a voltage is induced in secondary winding169 which is applied to relay 3WCTP picking up that relay. The relay3WCTP being a code following relay, it is operated instep with the 75code current applied to the section 3T. With relay 3WCTP operated toclose its contacts 61 and 110, then an inverse or feed back code pulseis supplied from battery B3B to the rails of the section 3T, thecurrentv pulse flowing from the positive terminal of battery 133Ethrough front'contacts 61 and 116 in series and wire 60 to rail 1b andthence from rail back by wire 57 to the negative terminal of batteryB3B. This inverse code thus supplied to the rails of :section 3T isreceived at the left-hand end of the section 3T to flow from rail 11;through wire 17, front contacts 16 and91 of the relays 4621 and 4RGZP,respectively, winding of relay SWCF,

the 75 code the relay 46K is energized through the decoding transformer4RDTdue to current being alternatciy supplied to the primary winding ofthe decoding transformer through contact 111 of relay 3WCF and thevoltages induced in the secondary winding of this decoding transformerbeing rectified at contact 112 of the code following relay. With relay4GK picked up energy is supplied to terminal 114 of the centralizedtraftic control equipment of station 2FS through the connc'ctionincluding front contact 113 of the relay 46K and front contact 115 ofrelay 4RGZP so that the centralized trafiic control equipment is madeactive to provide an indication code from station ZFS to the oflice ofthe centralized traflic control system for indicating that the signal 4Rhas been cleared.

It follows from the foregoing that the siding leaving signal 4R iscontrolled and indicated from the field station ZFS of the centralizedtraflic control system by use of normal and inverse coded track circuitcurrent of the 75 code, the polarity of the track circuit current beingopposite from that used for cascading through the block.

The operation of the apparatus as the train from the siding movesthrough the block to the location 6 is substantially the same as thatdescribed for the train advancing through this block from the main trackat location 2;

It, is to be pointed out, however, that as the train from the sidingmoves past signal 4R and enters the section 3'!" the code followingrelay 3ECF is shunted so that the relay 4WTP is deenergized and the codefollowing relay 4RCF is no longer operated by the coded current suppliedfrom section 41 with the result the signal 4R is restored to its stopposition. Also, as this train trails through the spring switch 3W, acontact 116 operatively connected to the switch as indicated by a dottedline is opened, causing a relay -RRG to be deenergized opening its frontcontact 117 and thus in turn deenergizing the relay 4RM. When this trainhas moved east and has vacated the section 31" and the spring switch hasassumed its normal position, the closing of the controller contact 116causes energy to be applied to a time element relay TER, the circuitextending from terminal B through back contacts 1M and 118 of thecontroller of the signal mechanisrn 4R6, contact 116, heater element 119of the relay TER and back contact 120 of relay eRRG to. terminal N. In aselected time interval the relay TER closes its contact 121 andcompletes a connection for picking up the relay 4RRG which opens thecircuit for the heater element of relay TER and completes the stickcircuit for relay 4RRG through the heater element, the arrangement beingsuch that this current is sufficient to retain the relay iRRG picked upbut insufficient to cause operation of the relay TER. Then, after 'therelay TER has assumed its normal position a circuit is completed for therelay 4RMj through the check contact 122 of relay TER and front contact117 or" the relay 4RRG. It follows that in a short period of time afterthe train has passed through the spring switch the apparatus is restoredto its normal position whereas the apparatus is not restored to itsnormal position during the short interval that the spring switch maymove toward its normal position between the car trucks.

l shall next assume that with the apparatus in its normal position thesignal 614A is to be cleared to permit a. westbound train to movethrough the block. Also, the take sliding signal 4L is to be operated toconvey to this train the instruction that it is to stop at switch SW andhand-throw the switch and move to the siding 2P8. Under this conditionthe operator sends a control code which at'station 6P8 causes positiveenergy tobe applied to a terminal 133 to which a signal controlrelayr6LAGZ.

is connected so that this relay is picked up in response to this controlcode and then retained energized due to a stick circuit including itsown front contact 134 and terminal 135 of the centralized .trafiiccontrol apparatus to which terminal energy is supplied through the usualform of circuit network. With the picking up of front contact'136 of therelay 6LAGZ, a circuit is prepared for the signal mechanism GLAG so thatthis mechanism is made ready to respond to coded track circuit energycascaded through the track circuits of the block.

v This control code of the centralized traffic control sys-. tem whenreceived at the station 2FS causes positive energy to be applied atterminal 137 to which relay 4LGZ is connected and this relay is pickedup and then retained energized over a circuit which includes its ownfront contact 138, back contact 139 of relay 4RGZ, front'contact 146 ofrelay 4G1 and back contact 141 of relay 468. With the relay 4LGZ thusselected, the relay. 4GZP is energized by the circuit including frontcontact 142 of the relay 4LGZ. The picking up of the relay 4GZPcompletes the circuit for relay 4G1 as previously explained and acircuit by which the code transmitting relay 3ECTP is operated by the1219GT coder at this location, the circuit extending from terminal B,through contact 143 of the coder 120CT, back contact 186- of relay4RGZP, front contact 37 of relay tGZP, front contact 38 of relay ZRMR,front contact 89 of relay, ZTR and winding of relay 3ECTP to terminal N.The operation of the coding relay 3ECTP causes current pulses of thev120 code rate to be supplied from battery B3W to the track circuit forthe section 3T through front contacts 14 and loofrelay i-GZP and backcontacts 91 and 92 of the relay ARGZP. This coded current is of thepolarity that causes the rail 1a to be positive with respect to the rail1b. .7

This trackcircuit current is by-passed from section 31 to section 4T bythe connection previously described. At the location of signal 5L, thecoded track circuit current is applied to the code following relay QECFthrough a connection that includes wire52, back contact 51 of relaySWFR, winding of relay 4ECF from rightto left, back contact 178 of relayeCTP, and Wire 53 to rail 16, the relay 4ECF being operated at the 120code rate. Operation of the contact member 149 of' relay' tfiCF causescurrent to be alternately supplied to the two portions of winding 150 ofdecoding transformer 4LD and voltages are induced in winding 151 whichare rectified by operation of the contact member 152 of the codefollowing relay and applied to a relay' 5LH .whcrewith that relay isenergized and picked up and retained picked up due to its slow releasecharacteristics.v Operation 10f the contact member 149 of the codefollowing relay 4ECF at the 120 code rate causes pulses to be suppliedto a decoding unit IZGDU so that a relay 4LH connected to that unit iseifectively energized and picked up. A signal circuit is now formed fromterminal B through front contact 153 of relay 4LH, winding of relay 4LGPand the lamp of signal 41. to terminal N. The parts are proportioned forthe lamp of the signal 4L to be illuminated and for the relay 4LGP to bepicked up. With the relay 4LGP picked up closing front contact 154, aconnection is completed by which voltages induced in winding 155 of thedecoding transformer LD are applied to winding 156 of anothertransformer 4L1)? causing corresponding voltages to be induced inwinding 157 of this latter transformer with the result that relay 4CTPconnected to the winding 157 is operated at the code rate of thevoltages. The parts are so proportioned that relay 4CTP is operated toclose its contacts 178 and 177 during the off code period of the trackcircuit current now supplied to section 4T. Thus, inverse code pulses ofthe 120 code rate are applied to the rails of section 4T from thebattery B4B, the connection including the positive terminal of batteryB4B, resistor 49, front contacts 178 and 177 in series, wire 158, backcontact 51 of relay SWFR, and wire 52 to rail and from rail 117 throughwire 53 to the negative terminal of battery B4B. These inverse codepulses of the 120 code rate when supplied to the rails of section 41 atsignal 5L are by-passed to the rails of section 3T and at the left-handend of the section 3T the pulses are supplied to the code followingrelay SWCF by the connection which extends from rail 1a through wire 19,front contact 14 of relay 4GZP, back contact 92 of relay 4RGZP, windingof relay 3WCF from right to left, back contact 90 of relay SECTP, backcontact 91 of relay l-RGZP, front contact 16 of relay 4GZP and wire 17to rail 117. With the code following relay 3WCF operated at the 120 coderate indication relay 46K is energized due to the energy applied to thewinding through the decoding transformer 4RDT and the contacts 111 and112 of the code following relay SWCF. With indication relay 46K pickedup a circuit is formed by which energy is applied to terminal 160 at thefield station 2FS, the connection including front contact 113 of relay46K and back contact 115 of the relay 4RGZP, and with energy thusapplied to terminal 160 the apparatus at the field station ZFS functionsin the usual manner to transmit an indication code to the ofiice of thecentralized trafiic control system indicating that the signal 4L hasbeen displayed.

Referring again to Fig. 1c, the picking up of the relay SLH in responseto the code pulses of the 120 code rate completes a circuit forenergizing the directional relay SEFR, the circuit including backcontact 161 of relay SWFR, front contact 163 of relay SLH and thewinding of relay SEFR. With the picking up of the directional relay SEFRclosing the front contact 164, a simple circuit is provided for the codetransmitter 75CT for operation thereof and another circuit is formed foroperating the coding relay SECT P at the 75 code rate, this lattercircuit including terminal B, contact 79 of the coder 75CT, back contact162 of relay SLGY, front contact 165 of relay SEFR and winding of relaySECTP to terminal N. Operation of the coding relay SECTP at the 75 codecauses current pulses to be supplied to the track circuit of section 5Tfrom battery BSW, the connection extending from the positive terminal ofbattery BSW through a resistor 166, winding of approach relay SWAE,front contact 167 of the coding relay SECTP, front contact 31 of relaySEFR, rail in and from rail 1b over wire 32 to the negative terminal ofthe battery BSW.

It is to be noted that although these current pulses flow in theapproach relay SWAE in the direction to pick up this polar relay, themagnitude of the pulses under normal conditions is insufficient to pickup the relay and the relay is picked up only when the magnitude of thepulses is increased in a manner to be described shortly.

The normal track circuit pulses of the 75 code rate thus supplied to thesection 5T are received at the right-v is picked up and retained pickedup due to its slow release feature.

Since the remote control relay 6LAGZ is picked up closing front contact136 as previously explained, the energization of the relay 6LH to closeits front contacts and 171 completes a circuit for the signal mechanismGLAG, the circuit being completed over the back contacts 172 and 173 ofrelay 6LD with the result that the signal 6LA is operated for the signalto display an approach indication and thereby permit the train to movepast signal 6LA into the block.

When this westbound train enters the section ST and is within a givendistance of the signal 5L, the code pulses supplied to the rails of thesection 5T are increased in magnitude due to the shunting out of therail impedance and this increased magnitude of the track circuit pulseswould cause the approach relay SWAE to be operated and operation of thiscontact 174 completes a simple circuit for a slow release approachrepeater relay SWAP and that relay is picked up and retained picked up.The closing of front contact 175 of the approach relay SWAP completes inturn a simple circuit for the lamp 176 of the signal 5L and this lamp isilluminated causing the signal 5L to display a red light. Thus, as thetrain approaches signal 5L it displays a red light. But, as previouslyexplained, the lamp for signal 4L is illuminated and there is conveyedto the train information that the train is to stop at the switch SW andhandthrow the switch and move to the passing siding.

When the head end of the train enters the section 4T, both the normaland inverse code pulses of the 120 code rate that are being supplied tothe section 4T are shunted. This causes the operation of the codefollowing relay 4ECF to cease and relays 4LH and 5LH to be released.

At location 2 the discontinuing of the inverse code pulses of the 120code rate causes the code following relay 3WCF to be no longer operatedwith the result that the indication relay 46K is deenergized andreleased. The opening of front contact 86 of indication relay 4GK opensthe stick circuit by which the relay 4GZP is retained energized and thisrelay is released to open its front contacts 14 and 16 with the resultthat the connection by which normal code pulses are being supplied tothe section 3T from the battery B3W is open and the supply of the pulsesis discontinued. It follows that when the train has moved to the passingsiding 2P8 and the switch is returned to its normal position, theapparatus is automatically restored to its normal condition.

The operation of the apparatus for clearing the signal 6LA to permit atrain on the main track to move through the block without taking sidingat switch 3W is substantially the same as the operation of the apparatusfor an eastbound train and the operation of the apparatus for thewestbound train will be apparent from an inspection of the drawingstaken in connection with the description of the operation of theapparatus for the eastbound train.

' It should be pointed out that when current pulses of the 180 code rateare received at location 2 from the track section 3T causing the relay180CP to be picked up closing its front contact 181 in the mannerpreviously explained, a simple circuit is formed by which energy isapplied to terminal 182 of the centralized traflic control field station2FS and which in turn would cause the centralized trafiic control systemto transmit a clear block indication to the oflice of the centralizedtrafiic control 15 system. Similarly, at location 6, the reception ofcurrent pulses of 180 code rate from the track section T causes therelay 180CP of the decoding unit at that location to be picked upclosing front contact 183 so that a simple circuit is formed by whichenergy is applied ,to terminal 184 of station 6FS and a clear blockindication is transmitted through the'centralized traffic control systemto the office.

It is to be noted that the relay 468 at fieldtstation 2FS can beenergized and picked up by operation of a normally open push button 179and relay 468 on picking up opening back contacts 141 and 146 opens thestick circuits for the relays 4LGZ, 4RGZ, 4GZP and 4RGZP, Thus this pushbutton provides means by which the signals 4R and 4L can be restored totheir normal position in ca'se of an emergency. 7

Although I have herein shown and described but one form of single trackrailway signal system using normally deenergized coded track circuitsembodying my invention,sit is to be understood that various changes andmodifications may be made therein within the scope of the appendedclaims without departing from the spirit and scope of my invention. f

Having thus described my invention, what I claim is:

1. In combination, a main track having a passing siding including afirst and a second track switch, a siding leaving signal'positioned togovern traffic moving from the siding through said first switch andhaving means operable to display a different indication for each of aplurality of different traflic conditions, said main track formed with afirst and a second track section which extend in opposite directionsfrom said first switch, traffic controlled means including a currentsource and code transmitting means operable to supply current ofdifferent codes according to different traffic conditions, said trafficcontrolled means having connections to said second track section at theend remote from said first switch; supply means including a currentsource and another code transmitting means operable to supply current ofa selected code, means including a circuit controller to at timesconnectsaid supply means to said first track section at the end remotefrom said first switch, a first code following relay connected to saidfirst track section at the endadjacent said first switch and responsiveto the code of the current supplied by said supply means; control meansincluding a second code following relay, a decoding device and a controlrelay for each of said traffic conditions; said decoding device andcontrol relays connected to the second code following relay to energizethe control relays according to the code of the current supplied to thesecond code following relay, means including contacts of said first codefollowing relay to connect at times said second code following relay tosaid second track section at the end adjacent said first switch toselectively engage said control relays according to the trafiic codesupplied by said traflic controlled means, and circuit means includingcontacts of said control relays to govern said siding leaving signal.

2. In combination, a main track having a passing siding including afirst and a second track switch, a siding leaving signal positioned togovern trafiic moving from the siding through said first switch andhaving means operable to display a different indication for each of aplurality of different trafiic conditions, said main track formed into,a first and a second track section which extend in opposite directionsfrom said first switch, traffic controlled means including a currentsource and code transmitting means operable to supply current ofdifferent code rates according to different traffic conditions, saidtraffic controlled means having connections to said second'track sectionat the end remote from said first switch, a waya side station adjacentsaid second track switch and having a remotely controlled relay and anindication relay, supply means'including a currentsource and anothercode transmitting means operable to supply current of a selectedcoderate; means including contacts of said remotely controlled relay toconnect said supply means to the rails of said first section adjacentsaid second switch, a first code following relay connectcdto the, railsof the first section adjacent the first track switch, said first codefollowing relay responsive to current of said selected code rate,control means including a second code following relay, decoding meansand control. relays one for each,

of the different trafiic conditions; said decoding means and controlrelays being connected to the second code following relay to selectivelyenergize the control relays according to the code rate of the currentsupplied to that code following relay, means including contacts of theto said signal and contacts of said first code following relay to supplyto said first section current of an inverse code of the code supplied bysaid supply means, another 7 code following relay connected tosaid firstsection adjacent said second switch responsive to said inverse codecurrent, and means including a contact of said another code followingrelay to energize said indication relay.

3. In combination with a stretch of main track over which traffic movesat times tothe east and having a passing siding and formed adjacentthesiding with a track section, said section being provided with a trackcircuit including a polar code following relay and an associateddecoding means at each end of the section, a main track signal locatedat the west end of said section and disposed to govern traffic throughthe section and to the east on the main track, a siding leaving signallocated at the east end of the siding and disposed to govern trafficmoving from the siding to the section and east on the main track, eachsaid signal having means operable to display a different indication foreach of a plurality of different traffic conditions, trafiic controlledmeans including a power source and code transmitting means havingconnections to the rails of the main track east ofsaid section andoperative to supply current of a selected polarity coded at differentcode rates according toIdifierent traffic conditions, circuit meansincluding contacts of the decoding means at the east end of said sectionand closed when the decoding means is deenergized to interconnect therails east of the section tothe rails at the 'east end of the section tosupply said coded current to the rails of the section, said codefollowing relays being poled for the relay at the west end of thesection to respond and the relay at the east end of the section not torespond to the polarity of the coded current of traflic codes thussupplied to said section, means including another power source, anothercode transmitting means and a remotely controlled contact connectedacross thera'ils at the west end of the section and operative to supplyat times current coded at a rate different from the traflic codes: saidanother source being poled to operate the code following. relay at theeast end of theisection but not the relay at the west end of thesection, another polar code following relay and associated decodingmeans, other circuit connections including contacts of the decodingmeans at the east end of the section closed when tha't decoding means isenergized to connect the rails east of saidisection to said another codefollowing relay, said another code following relay being poled torespond to the polarity ofsaid current of trafiic codes, means includingcontacts of the decoding means at the west end of; the section to governsaid main track signal, and means including, contacts of said decodingmeans associated with said another code following relay to govern saidsiding leaving signal. a a w 4. ln combination with astretchof maintrack over which traffic moves at times to the east and having a 17passing siding and formed adjacent the siding with a track section whichis provided with a track circuit including a code following relay and anassociated decoding means, said relay being connected across the railsat the east end of the section, a siding leaving signal located at theeast end of the siding and disposed to govern traffic moving from thesiding to the main track and east on said main track, said signal havingmeans operable to display an individual indication for each of aplurality of different traflic conditions, trafiic controlled meansincluding a power source and code transmitting means having connectionsto the rails of the main track east of said section and operative tosupply current of different .code rates according to different trafficconditions; means including a remotely controlled contact, another powersource and another code transmitting means connected across the rails atthe west end of said section and operative to supply current coded at arate different from said traffic code rates when said contact is closed;said code following relay being responsive to the code of the currentsupplied by said another power source, another code following relay andan associated decoding means including control relays, said controlrelays being selectively energized according to the code rate at whichsaid another code following relay is operated, means including contactsof the first mentioned decoding means and closed when that decodingmeans is energized to connect said another code following relay to therails east of said section to selectively energize said control relaysaccording to the traflic code of the current supplied by the trafiiccontrolled means, and means including contacts of said control relays tooperate said signal to display the indication corresponding to thetraffic code of the current supplied.

5. in combination with a stretch of main track over which trafiic movesat times to the east and having a passing siding and formed adjacent thesiding with a track section which is provided with a track circuitincluding a code following relay and an associated decoding means, saidrelay being connected across the rails at the east end of the section, asiding leaving signal located at the east end of the siding and disposedto govern trattic moving from the siding to the main track and east-onsaid main track, said signal having means operable to display anindividual indication for each of a plurality of ditferent trafficconditions, traffic controlled means including a power source and codetransmitting means having connections to the rails of the main trackeast of said section and operative to supply current of different coderates according to different trafiic conditions; means including aremotely controlled contact, another power source and another codetransmitting means connected across the rails at the west end of saidsection and operative to supply current of a normal code and having acode rate different from said trafiic code rates when said contact isclosed; said code following relay being responsive to the code of saidnormal code current, another code following relay and an associateddecoding means including control relays, said control relays beingselectively energized according to the traff c code rate at which saidanother code following relay is operated, means including contacts ofthe first mentioned decoding means and ciosed when that decoding meansis energized to connect said another code following relay to the railseast of said section to selectively energize said control relaysaccording to the traffic code of the current supplied by said trafiiccontrolled means; means including contacts of said control relays tooperate said signal according to the selection of the control relays,controller means operatively associated with said signal and having acontact closed when the signal is operated to permit a train to movefrom the siding; indication means including a power source, saidcontroller contact and a contact operated by the first mentioned codefollowing relay and connected across the rails adjacent the east end ofsaid section and operative to supply to the section an inverse codecurrent, another code following relay connected across the rails at thewest end of said section and responsive to said inverse code current,and an indication relay controlled by the last mentioned code followingrelay.

6. In combination with a stretch of main track over which trat'tic maymove either east or west and having a passing siding and formed with afirst and a second track section which extend along the siding and easttherefrom, the east track switch of said siding provided with a springswitch mechanism, a siding leaving signal located along the siding anddisposed to govern trafiic moving from the siding through said springswitch and east on the main track, a take siding signal located at theeastend of said second section and disposed when displayed to instruct atrain to hand-throw the switch and move into the siding, a track circuitfor each of said sections including a polar code following relayconnected across the rails at the east end of the associated section; astation at the west end of the siding and provided with a currentsource, a first and a second code transmitter and a first and a secondremotely controlled relay; means including said first code transmitter,said current source and a contact of said first remotely controlledrelay and connected across the rails at the west end of said firstsection and operative to supply coded current of a selected polarity ofa first code rate to the track circuit of said first section; said codefollowing relay of the first section poled to respond to the polarity ofthe current of said first code rate, circuit means including contactsclosed when said code following relay of the first section is operatedto operate said siding leaving signal; other means including saidcurrent source, said second. remotely controlledrelay and said secondcode transmitter connected across the rails at the west end of the firstsection and operative to supply current of a second code rate and of apolarity to which the code following relay of the first section does notrespond, means including contacts closed when the first section codefollowing relay is not operated to interconnect the track circuit of thefirst section to the track circuit of the second section, said codefollowing relay of the second section poled to respond to the polarityof the current of said second code rate, and means governed by thesecond section code following relay when operated to operate said takesiding signal. 7

7. In combination with a stretch of main track over which trafiic maymove either east or west and having a passing siding and formed with afirst and'af second track section which extend along the siding and easttherefrom, the east track-switch of said siding provided with a springswitch mechanism, a siding leaving signal located along the siding anddisposed to govern trafiic moving from the siding through said springswitch and east on ,the main track, a take siding signal located at theeast end of said second section and disposed when displayed to instructa train to hand-throw the switch and move into the siding, a trackcircuit for each of said sections including a polar code following relayat the east end of each of the sections, said track circuits beinginterconnected by contacts closed when the code following relay for theeast end of the first section is not operated; a station at the west endof the siding and including a first and a second remotely controlledrelay, 3. first and a second indication relay, a first and a second codetransmitter and a current source; means including said current source,contacts of said remotely controlled relays and a contact of said firstcode transmitter connected to the track circuit of said first sectionand operative to supply coded current of a first code and of a polarityse lected to be effective to operate the code following relay at theeast end of the first section; means controlled by said code followingrelay at the east end of thefirst section when operated to control saidsiding leaving signal; other means including said current source, othercontacts of said remotely controlled relays and a contact of said secondcode transmitter connected to the track circuit of the first section andoperative to supply" coded current of a second code and of a polarityselected to be ine'ife'ctive to operate the code following relay at theeast end of the first section but effective to operate the codefollowing relay at theeast end of said second section due to s'aidinterconnection of the track circuits; means Controlled by the codefollowing relay at the east end of the second section when operated tocontrol said take siding signal, circuit controlling contacts oneoperatively associated with each of said signals and closed when theassociated signal is operated; a first indication means including acurrent source, said circuit controlling'contact ofthe siding leavingsignal and a contact operated b'yithe code following relay at the eastend of the first section; said first indication means connected acrossthe rails of said first section and operative to supply an inversetcodecurrent of the first code rate, a second indication means including acurrent source, said circuit controlling conta'c't of the take sidingsignal and a contact operated by the code following relay at the eastend of said second section; said second indication means connectedacross the rails of the second section and operative tosupply inversecode current of said second code rate, a pole changing relay controlledby said remotely controlled relays, another polar code following relayconnected across the rails attthe west end of the first section throughconfacts of the remotely controlled relays and contacts of said polechanging relay to respond to said inverse code currents, and said firstand second indication relays 'se lectively controlled by the lastmentioned code following ?-Y-.

Q8, In combination with a stretch of main track over which'traflic maymove either east or West and having a passing sidingrand formed with afirst and a second track section which extend along the siding and easttherefrom, the east track switch for the siding being hand-thrown fortrains moving west, a take siding signal located at the east end of saidsecond section and disposed when displayed to instruct a train to moveto the siding, a track circuit for each of said sections including apolar code following relay connected across the rails at the east end ofthe associated section; a station at the west end of the siding providedwith a current source, a remotely controlled relay and a codetransmitter; said 'code transmitter. operable at a selected code rate,interconnections including contacts controlled by the code followingrelay at the east end of the first section to connect the track rails ofthe first section to the track rails of the second section when thatcode following relay is not following code; means including said currentsource, a contact of said remotely controlled relay and a contactof'said code transmitter connected "at times across the rails at thewest end of the first section and operative to supply current of a givenpolarity of said selected code, 'said code following relay at the eastend of said first section being poled to be nonresponsive to codedcurrent of said given polarity, said code following relay of said secondsection poled to respond to said coded current of said given polarity aspassed by said interconnection, decoding means including a relay and aunit having tuned inductance and capacitance governed by the codefollowing relay of the second section and effectively ener- 'gized inresponseto current of said selected code, and a t circuit including'acontact of said relay of the decoding unit to energize said take sidingsignal.

9. In combination witha stretch of track over which trains move ineither direction and having passing sidings and formed with a blockextending from a given end of a first passing siding along that sidingand to a second passing siding, said block being formed with tracksections provided with coded track circuits which use difier'ent codesselected to reflect different tratfic conditions, said track circuitsbeing provided with intercon- 1 nection's operable in either directionfor the code of one moving from the first siding through said block,said' signal having means'operable to display an individual signalaspect for each of a plurality of different trafiic conditions, meansincludinga selected one of the re motely controlled relays at thestation for the end of the block at said second siding effective whenenergized for causing current of a selected traffic code to be suppliedte-the track circuit adjacent that end of the block and cascadedtherefrom, means including a selected-one of the remotely controlledrelays at the station at said given end of said first'siding effectivewhen energized for causing current of a code dilferent from said trafliccodes to be supplied to the track circuit for the section adjacent thatend of the block and cascaded therefrom, means including a codefollowing relay and a first decoding means 7 connected to the trackcircuit for the section adjacent said opposite end of the first sidingresponsive to said difierent code and having contacts in theinterconnection of the track circuits to arrest the cascading of saidtrafiic code, a second code following relay and a second decod ingmeans, means including contacts of the first decoding means to connectsaid second code following relay to the track circuit at said oppositeend of the first passing sid: ing, aid second decoding means beingresponsive to said trafiic codes, and means governed by saidsecond'decoding means to control said siding leaving signal.

10. In combination with a stretch of main track over which trains maymove in either direction and having passing sidings and which stretchisformed with a block extending from a given end of a first siding alongsaid siding and to a second passing siding, said block being formed withtrack sections provided with coded track circuits which use difierentcodes selected to reflect different traflic conditions, said trackcircuits being interconnected to enable the code for the track circuitof a section to be cascaded and govern the code of the track circuit forthe adjacent section in either direction, wayside stations one adjacenteach end of said block and each station provided with control relayswhich are selectively energized, a siding leaving signal having meansoperable to display a clear and an approach signal indication'locatcd atthe end of said first siding opposite said given end and disposed togovern traffic moving from said first siding to the main track andthrough said block, means including a selected one of the control relaysof the station for the end of the block at said second siding efiectivewhen energized for causing current coded according to traffic conditionsto be supplied to the track circuit adjacent that end of the blockandtcascaded therefrom} means including a selected one'of the controlrelays of the station for the end of the block at said given end'of thefirst siding effective when energized for causing cur rent of a codepreselected to be different from said traffic codes to be supplied tothe track circuit adjacent'that end of the block and cascaded therefrom,means includingfia code following relay and a first decoding deviceconnected to the track circuit for the section adjacent said oppositeend of the first siding responsive to said preselected code and havingcontacts interposed in the interconnections of the track'circuits toarrest the cascading of said traffic code current, and a second 'codefollowing relay and a second decoding device responsive to said trafiiccodes connected to the track circuit adjacent a said opposite end of thefirst siding by contacts'of said first decoding device, and meansincluding contacts of said second decoding device for controlling saidsignal 11. In combination with a stretch of main track over i whichtrains may move in either direction and having passing' 'sidingsand'which stretch is formed with a' block extending from a given end ofa first siding along said siding and to a second passing siding, saidblock being formed with track sections provided with coded trackcircuits Which use different code rates selected to refiect differenttrafiic conditions, said track circuits being interconnected to enablethe code for the track circuit of a section to be cascaded and governthe code rate of the track circuit for the adjacent section in eitherdirection, way ide stations one adjacent each end of said block and eachstation provided with control relays which are selectiveiy energized andwith indicating devices efiective to provide an indication when energyis applied thereto, a siding leaving signal having means operable todisplay a clear and an approach indication located at the end of saidfirst siding opposite said given end and disposed to govern trafficmoving from said first siding to the main track and through said block,means including a selected one of the control relays of the station forthe end of the block at said second siding effective when energized forcausing current coded according to trafiic conditions to be supplied tothe track circuit adjacent that end of the biock and cascaded therefrom,means including a selected one of the relays of the station at saidgiven end of the first passing siding eifective when energized forcausing current of a normal code having a code rate different from saidtraific codes to be supplied to the track circuit adjacent that end ofthe block and cascaded therefrom, means including a first code followingrelay and a first decoding device connected to the track circuit for thesection adjacent said opposite end of the first siding responsive tosaid difierent normal code and having connections interposed in theinterconnection for the track circuits to arrest the cascading of saidtrafiic codes, a second code following relay and a second decodingdevice connected to the track circuit adjacent said opposite end of thefirst passing siding by contacts of said first decoding device andresponsive to said traflic code, means including contacts of said seconddecoding device to control said signal, means including a contactoperatively connected to said signal and a contact of said first codefollowing relay to generate and supply to the track circuit at saidopposite end of the first passing siding current of an inverse code forsaid normal code, means including another code following relay andanother decoding device connected to the track circuit adjacent saidgiven end of the first section responsive to said inverse code, andmeans including contacts of said another decoding device to supplyindication energy to the station at said given end of the first siding.

References Cited in the file of this patent UNITED STATES PATENTS2,315,887 Wallace Apr. 6, 1943 2,344,573 Van Horn Mar. 21, 19442,350,620 Judge June 6, 1944 2,357,518 Judge Sept. 5, 1944

